FDG-PET for detection of osseous metastases from malignant primary bone tumours: comparison with bone scintigraphy

Imaging pediatric bone sarcomas

Primary malignant bone tumors are rare and account for about 6% of all new pediatric cancer cases per year in the United States. Identification of the lesion not uncommonly occurs as a result of imaging performed for trauma. Clinical and standard imaging characteristics of the various tumor types are evolving in concert with treatment advancements and clinical trial regimens. This article reviews the 3 most common pediatric bone sarcomas-osteosarcoma, Ewing sarcoma, and chondrosarcoma-and their imaging as applicable to contemporary disease staging and monitoring, and explores the roles of evolving imaging techniques.

[Contribution of FDG-PET in the management of pediatric sarcomas in 2011]

FDG-PET has boomed in recent years for diagnosis, staging and the search for recurrence of a large number of tumors. This is particularly true for soft tissue sarcomas and musculoskeletal sarcomas, for which the first publications on the potential role of FDG-PET dating back to the early 1990s. The majority of published studies on adult sarcomas confer, possibly a mixed population. Studies dedicated to pediatrics population are much rarer. The "Standards, Options and Recommendations" of the French Federation of Anticancer Centers published in 2003 on "The use of FDG-PET in oncology" and make recommendations and expert advices as part sarcomas of adult patients. After a first part dedicated to the particular interpretation of FDG PET in children, the purpose of this paper is to review the potential contribution of this exam in the treatment of pediatric sarcomas.

Diffusion-weighted imaging (DWI) in musculoskeletal MRI: a critical review

Magnetic resonance imaging (MRI) is the mainstay of diagnosis, staging and follow-up of much musculoskeletal pathology. Diffusion-weighted magnetic resonance imaging (DWI) is a recent addition to the MR sequences conventionally employed. DWI provides qualitative and quantitative functional information concerning the microscopic movements of water at the cellular level. A number of musculoskeletal disorders have been evaluated by DWI, including vertebral fractures, bone marrow infection, bone marrow malignancy, primary bone and soft tissue tumours; post-treatment follow-up has also been assessed. Differentiation between benign and malignant vertebral fractures by DWI and monitoring of therapy response have shown excellent results. However, in other pathologies, such as primary soft tissue tumours, DWI data have been inconclusive in some cases, contributing little additional information beyond that gained from conventional MR sequences. The aim of this article is to critically review the current literature on the contribution of DWI to musculoskeletal MRI.

Diffusion-weighted imaging (DWI) in musculoskeletal MRI: a critical review

Magnetic resonance imaging (MRI) is the mainstay of diagnosis, staging and follow-up of much musculoskeletal pathology. Diffusion-weighted magnetic resonance imaging (DWI) is a recent addition to the MR sequences conventionally employed. DWI provides qualitative and quantitative functional information concerning the microscopic movements of water at the cellular level. A number of musculoskeletal disorders have been evaluated by DWI, including vertebral fractures, bone marrow infection, bone marrow malignancy, primary bone and soft tissue tumours; post-treatment follow-up has also been assessed. Differentiation between benign and malignant vertebral fractures by DWI and monitoring of therapy response have shown excellent results. However, in other pathologies, such as primary soft tissue tumours, DWI data have been inconclusive in some cases, contributing little additional information beyond that gained from conventional MR sequences. The aim of this article is to critically review the current literature on the contribution of DWI to musculoskeletal MRI.

Guidelines for paediatric bone scanning with 99mTc-labelled radiopharmaceuticals and 18F-fluoride

The purpose of these guidelines is to offer nuclear medicine teams a framework that could prove helpful in daily practice. The guidelines include information related to the indications, acquisition, processing and interpretation of bone scans in children, focusing primarily on (99m)Tc-labelled diphosphonate scintigraphy, and also recommendations with regard to the emerging use of PET with (18)F-fluoride.

PET imaging for pediatric oncology: an assessment of the evidence

Positron emission tomography (PET) has shown potential benefits when used in therapeutic clinical trials for children with cancer. However, existing trials are limited in scope with small numbers of patients and varied observations, making accurate conclusions about the usefulness of PET scanning impossible. This review examines PET and its applications in pediatric oncology. While evidence is limited, there appears to be a basis for rigorous evaluation of this imaging modality before widespread application without validation from clinical trials.

Impact of abdominopelvic CT on Ewing sarcoma management

RATIONALE AND OBJECTIVES

Abdominopelvic computed tomography (APCT) is often performed in patients with skeletal Ewing sarcoma family of tumors during initial staging and for subsequent clinical indications, such as metastasis surveillance; however, its clinical impact is unknown. The purpose of this study was to evaluate whether these computed tomographic examinations alter oncologic management and therefore patient outcomes.

MATERIALS AND METHODS

One hundred eight consecutive patients with skeletal Ewing sarcoma family of tumors seen from 1985 to 2008 were retrospectively reviewed to identify imaging workup, pathology, primary site, evidence of metastatic disease, and patient outcomes. Data were analyzed using Wilcoxon's rank sum tests.

RESULTS

Sixty-five of the 108 patients (60%) underwent 342 abdominopelvic computed tomographic examinations during a mean follow-up period of 8.9 years. During this time period, only one of the 65 patients (1.5%) who underwent APCT was discovered to have abdominal metastatic disease. There was no significant difference in the incidence of metastatic disease to the skeleton or chest between the groups without and with APCT (P = .10). There were 26 pelvic and lumbosacral primaries (24%) and 82 limb primaries (76%). Subgroup analysis performed on the 82 patients with limb primaries without (n = 36) and with (n = 46) APCT showed no significant differences in metastatic incidence to the skeleton or chest (P = .14).

CONCLUSIONS

This study indicates that APCT, associated with increased radiation exposure and health expenditure, has a limited role in initial staging and follow-up in patients with skeletal Ewing sarcoma, particularly in patients with limb primaries.

[Combined functional and morphological imaging of sarcomas: significance for diagnostics and therapy monitoring]

(18)F-fluorodeoxyglucose positron-emission tomography (FDG-PET) and especially hybrid FDG-PET/CT is becoming more and more accepted for the clinical management of adult and pediatric patients with sarcomas. By integrating the CT component the specificity in particular but also the sensitivity of the modality are improved further. With PET/CT a complete staging including the detection of lung metastases is feasible in a single examination. For patients with primary bone and soft tissue sarcomas FDG-PET/CT is utilized for diagnosis, staging and restaging, metabolic tumor grading, guidance of biopsies, detection of tumor recurrence and therapy monitoring. Furthermore, it has been demonstrated that FDG uptake of the tumor prior to treatment and changes of FDG uptake after therapy significantly correlate with histopathologic response and survival of patients. Therefore, PET and PET/CT have a prognostic value. In the future new perspectives of hybrid PET/CT imaging will arise by introducing novel radiotracers and combined functional imaging of tumor metabolism and perfusion. High resolution MRI is essential for local evaluation of the primary tumor and preoperative planning with assessment of possible infiltration of vascular or neural structures. Contrast-enhanced MRI remains a key tool in the diagnosis of recurrent disease, especially in tumors which are not hypermetabolic. Dynamic contrast-enhanced MR sequences can significantly contribute to therapy monitoring. More research is necessary to prospectively compare dynamic contrast-enhanced MRI and FDG-PET/CT for evaluation of local and recurrent diseases.

(18)F-FDG-PET and PET/CT for Evaluating Primary Bone Tumors

Imaging is critical for the proper evaluation of patients with primary tumors of bone. There is a growing role for (18)F-fluorodeoxyglucose PET and PET/computed tomography (CT) in the grading, staging, prognostication, evaluation of therapeutic response, and detection of recurrent disease in bone. These modalities can also be used to help differentiate benign from malignant disorders of bone.

PET/CT in primary musculoskeletal tumours: a step forward

Hybrid imaging with combined positron emission tomography/computed tomography (PET/CT) plays an important role in the staging and management of a wide variety of solid tumours. However, its use in the evaluation of musculoskeletal malignancy has not yet entered routine clinical practice. Cross-sectional imaging with magnetic resonance imaging (MR) and computed tomography have well-established roles but there is increasing evidence for the selective use of PET/CT in the management of these patients. The aims of this article are to review the current evidence and clinical applications of PET/CT in primary musculoskeletal tumours and discuss potential future developments using novel PET tracers and integrated PET/MR.

Role of 2-deoxy-2-[F-18] fluoro-D-glucose positron emission tomography in the management of bone and soft-tissue metastases

We retrospectively reviewed 71 histopathologically-confirmed bone and soft-tissue metastases of unknown origin at presentation. In order to identify the site of the primary tumour all 71 cases were examined with conventional procedures, including CT, serum tumour markers, a plain radiograph, ultrasound examination and endoscopic examinations, and 24 of the 71 cases underwent 2-deoxy-2-[F-18] fluoro-D-glucose positron emission tomography (FDG-PET). This detected multiple bone metastases in nine patients and the primary site in 12 of the 24 cases; conventional studies revealed 16 primary tumours. There was no significant difference in sensitivity between FDG-PET and conventional studies. The mean maximal standardised uptake value of the metastatic tumours was significantly higher than that of the primary tumours, which is likely to explain why FDG-PET did not provide better results. It was not superior to conventional procedures in the search for the primary site of bone and soft-tissue metastases; however, it seemed to be useful in the staging of malignancy.

The value of local treatment in patients with primary, disseminated, multifocal Ewing sarcoma (PDMES)

BACKGROUND

The value of local treatment in patients with primary, disseminated, multifocal Ewing sarcoma (PDMES) was investigated.

METHODS

We analyzed 120 patients registered into the European Ewing Tumor Working Initiative of National Groups (EURO-E.W.I.N.G. 99) trial at the trial center of Muenster from 1998 to 2006. Median age was 16.2 years. Local treatment of the primary tumor was surgery in 26 of 120 patients, surgery and radiotherapy in 21 patients, and definitive radiotherapy in 40 patients. For treatment of metastases, 6 of 120 patients received surgery; 9 patients, surgery and radiotherapy; and 33 patients, definitive radiotherapy. Forty-seven (39%) patients had local treatment of both the primary tumor and metastases, 41 (34%) patients of either the primary tumor or metastases, and 32 (27%) received no local therapy.

RESULTS

Event-free survival (EFS) at 3 years was 0.24 (95% CI, 0.16-0.33). Univariate analyses demonstrated the impact of local therapy given to the primary tumor: 3-year EFS was 0.25 with surgery, 0.47 with surgery and radiotherapy, 0.23 with radiotherapy, and 0.13 when no local therapy was administered (P < .001). Three-year EFS in PDMES was also influenced by the local treatment: surgery, 0.33; surgery and radiotherapy, 0.56; radiotherapy, 0.35; no local therapy, 0.16 (P = .003). Three-year EFS was 0.39 in patients who received local treatment of both primary tumor and PDMES, compared with 0.17 in patients with any local treatment of either primary tumor or PDMES and 0.14 in patients with no local therapy (P < .001). Multivariate analysis showed absence of local treatment to be the major risk factor (HR = 2.21; P = .027; n = 20).

CONCLUSIONS

Local therapy of involved sites is important for patients with PDMES and should complement systemic treatment whenever possible.

Utilization of positron emission tomography in the management of patients with sarcoma

PURPOSE OF REVIEW

18F-fluorodeoxyglucose positron emission tomography (18F-FDG-PET) is being used with increased frequency in the care of patients with sarcoma. In this review, the recent literature covering all aspects of PET imaging in the management of patients with soft tissue and bone sarcomas will be discussed.

RECENT FINDINGS

In a prospective multicenter study, PET imaging accurately detected primary tumors as well as lymph node and bone metastases in patients with sarcoma. Limitations in detecting lung metastasis can be overcome by using a hybrid PET/CT scanner. In patients with neurofibromatosis, 18F-FDG-PET demonstrated its application to detect and monitor for the malignant transformation of neurofibromas. Changes in tumor 18F-FDG uptake correlate significantly with histopathologic response and survival in patients with sarcoma.

SUMMARY

PET imaging is emerging as an important imaging modality in the management of patients with sarcoma. Its applications include tumor grading, staging, therapeutic monitoring, and prognostication in adult and pediatric populations.

PET-CT imaging in pediatric oncology

Positron emission tomography (PET)-computed tomography (CT) is emerging as a valuable tool for assessing a wide variety of pediatric malignancies, including lymphomas, soft-tissue tumors, and bone sarcomas. PET-CT may provide information that is not apparent on conventional imaging performed to stage these diseases and monitor their response to treatment. The use of PET-CT in children requires an awareness of the technical and logistical issues unique to this patient population. In addition, interpretation of pediatric PET-CT imaging requires familiarity with aspects of pediatric anatomy and physiology that differ from those of adults. In this article, the technical considerations in performing pediatric PET-CT, pitfalls in the diagnostic use of PET-CT in children, and current and emerging applications of PET-CT in pediatric oncology are reviewed.

Guidelines for 18F-FDG PET and PET-CT imaging in paediatric oncology

OBJECTIVE

The purpose of these guidelines is to offer to the nuclear medicine team a framework that could prove helpful in daily practice. These guidelines contain information related to the indications, acquisition, processing and interpretation of (18)F-fluorodeoxyglucose positron emission tomography ((18)F-FDG PET) in paediatric oncology. The Oncology Committee of the European Association of Nuclear Medicine (EANM) has published excellent procedure guidelines on tumour imaging with (18)F-FDG PET (Bombardieri et al., Eur J Nucl Med Mol Imaging 30:BP115-24, 2003). These guidelines, published by the EANM Paediatric Committee, do not intend to compete with the existing guidelines, but rather aim at providing additional information on issues particularly relevant to PET imaging of children with cancer.

CONCLUSION

The guidelines summarize the views of the Paediatric Committee of the European Association of Nuclear Medicine. They should be taken in the context of "good practice" of nuclear medicine and of any national rules, which may apply to nuclear medicine examinations. The recommendations of these guidelines cannot be applied to all patients in all practice settings. The guidelines should not be deemed inclusive of all proper procedures or exclusive of other procedures reasonably directed to obtaining the same results.

PET and PET/CT in Pediatric Sarcomas

Because of the rarity of pediatric bone and soft tissue malignancies, it is difficult to validate the role of emerging imaging technologies in their management. The growing body of literature regarding the use of PET and PET/CT in children supports the continued investigation of this modality in the management of pediatric sarcomas. This article reviews the current literature regarding FDGPET imaging in the management of pediatric sarcomas and presents important pitfalls in PET/CT imaging of these patients that the author, her colleagues, and others have encountered.

The additional value of CT images interpretation in the differential diagnosis of benign vs. malignant primary bone lesions with 18F-FDG-PET/CT

OBJECTIVE

To evaluate the value of a dedicated interpretation of the CT images in the differential diagnosis of benign vs. malignant primary bone lesions with 18 fluorodeoxyglucose-positron emission tomography/computed tomography (18F-FDG-PET/CT).

MATERIALS AND METHODS

In 50 consecutive patients (21 women, 29 men, mean age 36.9, age range 11-72) with suspected primary bone neoplasm conventional radiographs and 18F-FDG-PET/CT were performed. Differentiation of benign and malignant lesions was separately performed on conventional radiographs, PET alone (PET), and PET/CT with specific evaluation of the CT part. Histology served as the standard of reference in 46 cases, clinical, and imaging follow-up in four cases.

RESULTS

According to the standard of reference, conventional 17 lesions were benign and 33 malignant. Sensitivity, specificity, and accuracy in assessment of malignancy was 85%, 65% and 78% for conventional radiographs, 85%, 35% and 68% for PET alone and 91%, 77% and 86% for combined PET/CT. Median SUV(max) was 3.5 for benign lesions (range 1.6-8.0) and 5.7 (range 0.8-41.7) for malignant lesions. In eight patients with bone lesions with high FDG-uptake (SUV(max) >or= 2.5) dedicated CT interpretation led to the correct diagnosis of a benign lesion (three fibrous dysplasias, two osteomyelitis, one aneurysmatic bone cyst, one fibrous cortical defect, 1 phosphaturic mesenchymal tumor). In four patients with lesions with low FDG-uptake (SUV(max) < 2.5) dedicated CT interpretation led to the correct diagnosis of a malignant lesion (three chondrosarcomas and one leiomyosarcoma). Combined PET/CT was significantly more accurate in the differentiation of benign and malignant lesions than PET alone (p = .039). There was no significant difference between PET/CT and conventional radiographs (p = .625).

CONCLUSION

Dedicated interpretation of the CT part significantly improved the performance of FDG-PET/CT in differentiation of benign and malignant primary bone lesions compared to PET alone. PET/CT more commonly differentiated benign from malignant primary bone lesions compared with conventional radiographs, but this difference was not significant.

Imaging guidelines for children with Ewing sarcoma and osteosarcoma: a report from the Children's Oncology Group Bone Tumor Committee

The Children's Oncology Group (COG) is a multi-institutional cooperative group dedicated to childhood cancer research that has helped to increase the survival of children with cancer through clinical trials. These clinical trials include a standardized regimen of imaging examinations performed prior to, during, and following therapy. This article presents imaging guidelines developed by a multidisciplinary group from the COG Bone Tumor Committee. These guidelines provide both required and recommended studies. Recommended examinations may become required in the future. These guidelines should be considered a work in progress that will evolve with advances in imaging and childhood cancer research.

Use of positron emission tomography for staging, preoperative response assessment and posttherapeutic evaluation in children with Wilms tumour

PURPOSE

To evaluate FDG-PET for staging, grading, preoperative response assessment and posttherapeutic evaluation in children with Wilms tumour (WT).

METHODS

In this study, 23 FDG-PET examinations in 12 paediatric patients (female, n = 5; male, n = 7; age, 1-19 years) with WT (primary, n = 9; relapsed, n = 3) were analysed. All patients were examined with conventional imaging methods (CIM) according to the SIOP2001/GPOH trial protocol. Additionally, FDG-PET/PET-CT was performed for staging (n = 12), preoperative response assessment (n = 6) and posttherapeutic evaluation (n = 5). Imaging results of FDG-PET and CIM were analysed regarding the accuracy in tumour visualisation, impact on therapeutic management and preoperative response assessment, with clinical follow-up and histopathology as the standard of reference.

RESULTS

FDG-PET and CIM showed concordant results for staging of primary WT, whereas FDG-PET was superior in 1/3 cases with recurrent WT. Concerning histological differentiation, one case with anaplastic WT had an standard uptake value (SUV) of 12.3, which was remarkably higher than the average SUV in the eight cases with intermediate risk histology. No parameter analysed for PET or CIM was reliably predictive for histological regression or clinical outcome. After completion of therapy, FDG-PET was superior to CIM in 2/5 cases in detecting residual disease with therapeutic relevance.

CONCLUSION

FDG-PET does not provide additional information to the traditional imaging work-up for staging WT patients, preoperative response assessment and clinical outcome. FDG-PET was advantageous in ruling out residual disease after completion of first line treatment and in pretherapeutic staging of relapse patients. Furthermore, there seems to be a good correlation of initial SUV and histological differentiation.

Use of FDG-PET in differentiating benign from malignant compression fractures

OBJECTIVE

The objective was to evaluate the use of fluorodeoxyglucose positron emission tomography (FDG-PET) in differentiating benign from malignant compression fractures.

PATIENTS AND METHODS

In a retrospective analysis, we identified 33 patients with 43 compression fractures who underwent FDG-PET. On FDG-PET the uptake pattern was recorded qualitatively and semiquantitatively and fractures were categorized as benign or malignant. Standardized uptake values (SUV) were obtained. MRI, CT, and biopsy results as well as clinical follow-up for 1-3 years served as standards of reference. The Student's t test was used to determine whether there was a statistically significant difference between the SUV for benign and malignant compression fractures.

RESULTS

There were 14 malignant and 29 benign compression fractures, including 5 acute benign fractures. On FDG-PET, 5 benign fractures were falsely classified as malignant (false-positive). Three of these patients underwent prior treatment with bone marrow-stimulating agents. There were two false-negative results. Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of FDG-PET in differentiating benign from malignant compression fractures were 86%, 83%, 84%, 71%, and 92% respectively. The difference between SUV values of benign and malignant fractures was statistically significant (1.9 +/- 0.97 for benign and 3.9 +/- 1.52 for malignant fractures, p < 0.001). SUV of benign acute and chronic fractures were not statistically significant.

CONCLUSION

Fluorodeoxyglucose positron emission tomography is useful in differentiating benign from malignant compression fractures. Therapy with bone marrow-stimulating agents can mimic malignant involvement.

Bone and soft-tissue sarcoma: preoperative staging with fluorine 18 fluorodeoxyglucose PET/CT and conventional imaging

PURPOSE

To retrospectively compare the diagnostic accuracy of positron emission tomography (PET)/computed tomography (CT), PET, conventional imaging, and combined PET/CT and conventional imaging for tumor staging of bone and soft-tissue sarcomas, by using histologic or follow-up imaging findings as the reference standard.

MATERIALS AND METHODS

Institutional review board approval was received for this HIPAA-compliant study; informed consent was obtained. Integrated PET/CT was performed in 117 patients (69 male patients, 48 female patients; mean age, 42 years +/- 21 [standard deviation]; range, 9-86 years). Conventional imaging consisted of magnetic resonance imaging of the primary site, chest radiography, whole-body contrast material-enhanced CT, and bone scintigraphy. A total of four reviewers assessed all images. Overall and T staging were evaluated in 69 (59%) patients who underwent surgical removal of the primary tumors and had pathologically proved results. N and M staging were evaluated in all patients, and their reference methods were based on histologic findings (n = 101) and follow-up CT findings (n = 16).

RESULTS

Interpretations based on combined PET/CT and conventional imaging findings correctly staged tumors in 60 (87%) of 69 patients, overstaged tumors in eight (12%) patients, and understaged tumors in one (1%) patient. Overall staging accuracy of combined PET/CT and conventional imaging was significantly higher than that at PET (P < .0001). Combined PET/CT and conventional imaging resulted in correct N staging in 114 (97%) of 117 patients and M staging in 109 (93%) of 117 patients. Combined PET/CT and conventional imaging helped reduce overstaging in three (4%) patients and helped change tumor diagnosis from unresectable to resectable in two (2%) patients compared with PET/CT.

CONCLUSION

The combination of PET/CT and conventional imaging is accurate in preoperative staging of bone and soft-tissue sarcoma.

Positron emission tomography for staging of pediatric sarcoma patients: results of a prospective multicenter trial

PURPOSE

The objective of this study was to evaluate the impact of positron emission tomography (PET) using fluorine-18-fluorodeoxyglucose (FDG) for initial staging and therapy planning in pediatric sarcoma patients.

PATIENTS AND METHODS

In this prospective multicenter study, 46 pediatric patients (females, n = 22; males, n = 24; age range, 1 to 18 years) with histologically proven sarcoma (Ewing sarcoma family tumors, n = 23; osteosarcoma, n = 11; rhabdomyosarcoma, n = 12) were examined with conventional imaging modalities (CIMs), including ultrasound, computed tomography (CT), magnetic resonance imaging, and bone scintigraphy according to the standardized algorithms of the international therapy optimization trials, and whole-body FDG-PET. A lesion- and patient-based analysis of PET alone and CIMs alone and a side-by-side (SBS) analysis of FDG-PET and CIMs were performed. The standard of reference consisted of all imaging material, follow-up data (mean follow-up time, 24 +/- 12 months), and histopathology and was determined by an interdisciplinary tumor board.

RESULTS

FDG-PET and CIMs were equally effective in the detection of primary tumors (accuracy, 100%). PET was superior to CIMs concerning the correct detection of lymph node involvement (sensitivity, 95% v 25%, respectively) and bone manifestations (sensitivity, 90% v 57%, respectively), whereas CT was more reliable than FDG-PET in depicting lung metastases (sensitivity, 100% v 25%, respectively). The patient-based analysis revealed the best results for SBS, with 91% correct therapy decisions. This was significantly superior to CIMs (59%; P < .001).

CONCLUSION

In staging pediatric sarcoma, subsidiary FDG-PET scanning depicts important additional information and has a relevant impact on therapy planning when analyzed side-by-side with CIMs.

Positron emission tomography/computed tomography with 18fluoro-deoxyglucose in the detection of local recurrence and distant metastases of pediatric sarcoma

BACKGROUND

Combined positron emission tomography with (18)fluoro-deoxyglucose and computed tomography (FDG-PET/CT) has been used in the diagnosis and staging of various malignancies, but their use in the management of pediatric sarcomas is less well defined. The potential role of FDG-PET/CT in the diagnosis of local recurrence and distant metastases of pediatric sarcomas was investigated.

PROCEDURE

Nineteen children (aged 2-21) with sarcoma (9 Ewing sarcoma, 3 osteogenic sarcoma, 7 rhabdomyosarcoma) were evaluated between January 2000 and December 2005 by FDG-PET/CT for suspected local relapse or distant metastases. The results of 21 FDG-PET studies, 16 CT scans, 9 magnetic resonance imaging (MRI) studies, and 7 bone scans (BSs) were compared with surgical pathology or clinical follow-up for at least 3 months.

RESULTS

FDG-PET detected local relapse in all seven patients and distant metastases in 10/13 (77%). FDG-PET/CT and CT/MRI/BS results were discordant in eight patients. FDG-PET/CT was the only modality that detected distant metastases in two patients. PET/CT was true negative and excluded disease in three patients with abnormal CT/BSs and was false negative in three patients with distant metastases.

CONCLUSION

FDG-PET/CT may be useful and complementary to other imaging modalities for the detection of recurrent pediatric sarcomas, especially at the primary site. Its potential advantages and limitations compared with conventional imaging modalities need to be further investigated in larger homogenous patient groups.

PET and PET/CT in pediatric oncology

18F-fluorodeoxyglucose positron emission tomography (FDG-PET) and FDG-PET/computed tomography (CT) are becoming increasingly important imaging tools in the noninvasive evaluation and monitoring of children with known or suspected malignant diseases. In this review, we discuss the preparation of children undergoing PET studies and review radiation dosimetry and its implications for family and caregivers. We review the normal distribution of 18F-fluorodeoxyglucose (FDG) in children, common variations of the normal distribution, and various artifacts that may arise. We show that most tumors in children accumulate and retain FDG, allowing high-quality images of their distribution and pathophysiology. We explore the use of FDG-PET in the study of children with the more common malignancies, such as brain neoplasms and lymphomas, and the less-common tumors, including neuroblastomas, bone and soft-tissue sarcomas, Wilms' tumors, and hepatoblastomas. For comparison, other PET tracers are included because they have been applied in pediatric oncology. Multiple multicenter trials are underway that use FDG-PET in the management of children with neoplastic disease; these studies should give us greater insight into the impact FDG-PET can make in their care. PET is emerging as an important diagnostic imaging tool in the evaluation of pediatric cancers. The recent advent of dual-modality PET-computed tomography (PET/CT) imaging systems has added unprecedented diagnostic capability by revealing the precise anatomical localization of metabolic information and metabolic characterization of normal and abnormal structures. The use of CT transmission scanning for attenuation correction has shortened the total acquisition time, which is an especially desirable attribute in pediatric imaging. Moreover, expansion of the regional distribution of the most common PET radiotracer, FDG, and the introduction of mobile PET units have greatly increased access to this powerful diagnostic imaging technology. Here, we review the clinical applications of PET and PET/CT in pediatric oncology. General considerations in patient preparation and radiation dosimetry will be discussed.

Accuracy of 18F fluorodeoxyglucose positron emission tomography/computed tomography in staging of pediatric sarcomas

The present study was conducted to clarify the diagnostic accuracy of 18F-fluoro-2-deoxy-D-glucose (18FDG) positron emission tomography (PET)/computed tomography (CT) in the staging in pediatric sarcomas. Fifty pediatric patients with histologically proven sarcomas who underwent 18FDG PET/CT before treatment were evaluated retrospectively for the detection of nodal and distant metastases. Diagnostic accuracy of 18FDG PET/CT in detecting nodal and distant metastases was compared with that of 18FDG PET and conventional imaging (CI). The images were reviewed and a diagnostic consensus was reached by 3 observers. REFERENCE standard was histologic examination in 15 patients and confirmation of an obvious progression in size of the lesions on follow-up examinations. Nodal metastasis was correctly assessed in 48 patients (96%) with PET/CT, in contrast to 43 patients (86%) with PET, and 46 patients (92%) with CI. Diagnostic accuracies of nodal metastasis in 3 modalities were similar. Using PET/CT, distant metastasis was correctly assigned in 43 patients (86%), whereas interpretation based on PET alone or CI revealed distant metastasis in 33 patients (66%) and 35 patients (70%), respectively. Diagnostic accuracy of distant metastasis with PET/CT was significantly higher than that of PET (P=0.002) or CI (P=0.008). False negative results regarding distant metastasis by PET/CT in 7 patients (14%) were caused by subcentimetric lesions (n=4), bone marrow lesion (n=2), and soft tissue lesions (n=1). PET/CT is more accurate and probably more cost-effective than PET alone or CI regarding distant metastasis in pediatric sarcomas.

MRI and (18)FDG-PET in the assessment of bone marrow infiltration of the spine in cancer patients

The aim of this study was to evaluate the diagnostic value of MRI and (18)FDG-PET in bone marrow infiltration of the spine due to metastases of solid tumours and lymphoma in cancer patients. In 35 cancer patients (solid tumours n = 26, lymphoma n = 9) MRI of the spine and (18)FDG-PET were reviewed and the detectability of metastases, infiltration of the spine, extent of disease, and therapeutic implications were compared. In 8/35 cases (23%) imaging technique showed concordantly no bone marrow infiltration. In 19/35 patients (54%), both MRI and (18)FDG-PET revealed bone marrow infiltration of the axial skeleton. In 12/19 patients (63%), MRI showed more extensive disease which lead to subsequent therapy. The imaging findings of MRI and (18)FDG-PET were discordant in 8/35 cases (23%). (18)FDG-PET was false positive in two patients. In six patients, (18)FDG-PET failed to detect bone metastases and bone marrow infiltration of the spine, which was detected by MRI and proven by clinical follow-up with subsequent therapy in two cases. MRI is more sensitive and specific than (18)FDG-PET detecting bone marrow metastases and infiltration of the spine and has a great impact in staging cancer patients.

Chemotherapy response is an important predictor of local recurrence in Ewing sarcoma

BACKGROUND

Local recurrence in Ewing sarcoma is associated with a poor prognosis. The purpose of the study was to determine the factors that predict local recurrence after surgical treatment of the primary tumor.

METHODS

Between 1990 and 2001, 64 patients underwent surgical resection of Ewing sarcoma. Surgical margins were assessed histologically and radiologically. Response to preoperative chemotherapy was determined by detailed specimen mapping. Local recurrence-free survival (LRFS) was calculated by Kaplan-Meier analysis. Multivariate analysis was performed with the Cox proportional hazards model.

RESULTS

A number of factors were found to be associated with local recurrence on univariate analysis. Patients with a good response to chemotherapy (> or = 90% tumor necrosis), had superior LRFS at 5 years (86% vs 51%, P = .015). Central site of disease was associated with an increased rate of recurrence. The LRFS at 5 years was 50% for the chest wall, 74% for pelvic/scapular, and 86% for extremity tumors (P = .083). Positive surgical margin was not a strong predictor of recurrence (P = .72). A critical analysis of minimal surgical margin based on preoperative magnetic resonance imaging (MRI) and computed tomography (CT) scans also failed to reveal an association between margin and local recurrence. In multivariate analysis, the 2 independent predictors of local recurrence were histological response to chemotherapy and central site of disease.

CONCLUSION

Local recurrence after surgical resection is a complex phenomenon. An important predictive factor is the response to chemotherapy. In the current study, this seems to have the largest impact. Central site of disease may be a second independent predictive factor.

Role for positron emission tomography in skeletal diseases

Imaging plays a prominent role in the diagnosis and management of rheumatic diseases. Conventional imaging methods provide high-resolution structural information but usually fail to distinguish between active lesions and residual changes. Positron emission tomography (PET) with the tracer 18F-fluorodeoxyglucose (18F-FDG) was recently introduced into clinical practice as a means of obtaining information on both structure and metabolic activity. 18F-FDG-PET is widely used in oncology and may be valuable in patients with infections or inflammatory diseases, most notably vasculitis. Although encouraging results have been published, the number of studies remains small, as 18F-FDG-PET is an expensive investigation that is not available everywhere. Further work is needed to determine the cost-effectiveness ratio of 18F-FDG-PET in patients with infections or inflammatory diseases. Imaging plays a prominent role in the diagnosis and management of many musculoskeletal diseases. Although considerable progress has been made recently, the structural information supplied by conventional imaging methods is inadequate in some patients. Positron emission tomography (PET) after injection of 18fluorodeoxyglucose (18F-FDG) provides information on tissue metabolism. The usefulness of 18F-FDG-PET in oncology is now widely recognized. Other uses are emerging, in part thanks to the development of new cameras that combine dedicated detectors and an X-scanner in order to ensure accurate three-dimensional localization of metabolically active lesions. However, the exact role for 18F-FDG-PET needs to be studied in larger populations of patients.

Multidisciplinary approach to diagnosis and management of osteosarcoma - a review of the St Vincent's Hospital experience

Background

Osteosarcoma is the most common primary malignant bone tumour in children and young adults. Despite advances in the diagnosis and management of osteosarcoma, there have been few recent studies describing the experiences of tertiary referral centres. This paper aims to describe and discuss the clinical features, pre-operative work-up, management and outcomes of these patients at St Vincent's Hospital (Melbourne, Australia).

Methods

Retrospective study of fifty-nine consecutive patients managed for osteosarcoma at St Vincent's Hospital between 1995 and 2005.

Results

Median age at diagnosis was 21 (range, 11–84) years. Gender distribution was similar, with thirty-one male and twenty-eight female patients.

Twenty-five patients had osteosarcoma in the femur, eleven each were located in the humerus and tibia, six were identified in the pelvis, and one each in the clavicle, maxilla, fibula, sacrum, ulna and radius.

Pre-operative tissue diagnosis of osteosarcoma was obtained through computed tomography-guided percutaneous biopsy in over ninety percent of patients.

Following initial therapy, over fifty percent of patients remained relapse-free during the follow-up period, with twelve percent and twenty-seven percent of patients documented as having local and distant disease recurrence, respectively. Of patients with recurrent disease, sixty-two percent remained disease-free following subsequent surgical intervention (most commonly, pulmonary metastatectomy).

Conclusion

Patient outcomes can be optimised through a multidisciplinary approach in a tertiary referral centre. At St Vincent's Hospital, survival and relapse rates of patients managed for osteosarcoma compare favourably with the published literature.

Staging performance of carbon-11 choline positron emission tomography/computed tomography in patients with bone and soft tissue sarcoma: comparison with conventional imaging

The present study was conducted to compare the diagnostic accuracy between carbon-11 choline (11C-choline) positron emission tomography (PET)/computed tomography (CT) and conventional imaging for the staging of bone and soft tissue sarcomas. Sixteen patients who underwent 11C-choline PET/CT prior to treatment were evaluated retrospectively for staging accuracy. Conventional imaging methods consisted of 99,mTc-hydroxymethylene diphosphonate bone scintigraphy, chest CT and magnetic resonance imaging of the primary site. The images were reviewed and a consensus was reached by two board-certified radiologists who were unaware of any clinical or radiological information using hard-copy films and multimodality computer platform. Tumor stage was confirmed by histological examination and/or by an obvious progression in number and/or size of the lesions on follow-up examinations. Reviewers examining both 11C-choline PET/CT and conventional imaging classified T stage in all patients. Interpretation based on 11C-choline PET/CT, the Node (N) stage was correctly diagnosed in all patients, whereas the accuracy of conventional imaging in N stage was 63%. Tumor Node Metastasis (TNM) stage was assessed correctly with 11C-choline PET/CT in 15 of 16 patients (94%) and with conventional imaging in eight of 16 patients (50%). The overall TNM staging and N staging accuracy of 11C-choline PET/CT were significantly higher than that of conventional imaging (P < 0.05). 11C-choline PET/CT is more accurate than conventional imaging regarding clinical staging of patients with bone and soft tissue sarcomas. A whole body 11C-choline PET/CT might be acceptable for imaging studies of tumor staging prior to treatment.

Role of PET/PET-CT in the management of sarcomas

Positron emission tomography (PET) is a functional diagnostic imaging technique that provides very different information from that obtainable with other imaging modalities. The most widely used radiotracer is F-18 fluoro-2-deoxy-D-glucose (FDG), which is an analog of glucose. The FDG uptake in cells is directly proportional to glucose metabolism, which is increased many times in malignant cells. FDG-PET is now the standard of care in initial staging, monitoring the response to therapy and management of various cancers (e.g., breast cancer, lung cancer and lymphoma). However, the paucity of anatomical landmarks on PET images makes a consistent hardware fusion to anatomical cross-sectional data extremely useful. The introduction of combined PET-computer tomography (CT) scanners, which provide not only functional, but also structural information leading to a detection of subcentimeter lesions, made this technique useful in the early detection of the disease process and decreasing false-positive lesions. The aim of this article is to review the clinical applications (i.e., diagnosis, staging, evaluation of treatment response and restaging) using PET in patients with bone and soft-tissue sarcoma.

Successful high-resolution animal positron emission tomography of human Ewing tumours and their metastases in a murine xenograft model

PURPOSE

As primary osseous metastasis is the main adverse prognostic factor in patients with Ewing tumours, a NOD/scid mouse model for human Ewing tumour metastases has been established to examine the mechanisms of metastasis. The aim of this study was to evaluate the feasibility of diagnostic molecular imaging by small animal PET in this mouse model.

METHODS

Human Ewing tumour cells were transplanted into immune-deficient NOD/scid mice via s.c injection (n=17) or i.v. injection (n=17). The animals (mean weight 23.2 g) were studied 2-7 weeks after transplantation using a submillimetre resolution animal PET scanner. To assess glucose utilisation and bone metabolism, mice were scanned after intravenous injection of 9.6 MBq (mean) 2-[(18)F]fluoro-2-deoxy-D: -glucose (FDG) or 9.4 MBq (mean) [(18)F]fluoride. Whole-body PET images were analysed visually and semi-quantitatively [%ID/g, tumour to non-tumour ratio (T/NT)]. Foci of pathological uptake were identified with respect to the physiological organ uptake in corresponding regions.

RESULTS

Subcutaneously transplanted Ewing tumours demonstrated a moderately increased glucose uptake (median %ID/g 2.5; median T/NT 2.2). After i.v. transplantation, the pattern of metastasis was similar to that in patients with metastases in lung, bone and soft tissue. These metastases showed an increased FDG uptake (median %ID/g 3.6; median T/NT 2.7). Osseous metastases were additionally visible on [(18)F]fluoride PET by virtue of decreased [(18)F]fluoride uptake (osteolysis; median %ID/g 8.4; median T/NT 0.59). Metastases were confirmed immunohistologically.

CONCLUSION

Diagnostic molecular imaging of Ewing tumours and their small metastases in an in vivo NOD/scid mouse model is feasible using a submillimetre resolution PET scanner.

Utility of positron emission tomography in sarcomas

PURPOSE OF REVIEW

Positron emission tomography using [18F]fluoro-2-deoxy-D-glucose has been studied as a tool to help predict the malignant potential of sarcomas, prognosis of patients and response to chemotherapy, and to detect disease recurrence. Recent developments in the use of [18F]fluoro-2-deoxy-D-glucose positron emission tomography in the clinical management of patients with suspected or diagnosed sarcomas are presented.

RECENT FINDINGS

[18F]fluoro-2-deoxy-D-glucose positron emission tomography should not be used in lieu of histology to diagnose sarcomas, but may aid in biopsy planning. [18F]fluoro-2-deoxy-D-glucose positron emission tomography should not replace magnetic resonance imaging and computed tomography imaging for staging or surveillance. In soft tissue sarcomas, [18F]fluoro-2-deoxy-D-glucose uptake correlates with histologic grade and risk of tumor recurrence. Reduction in [18F]fluoro-2-deoxy-D-glucose uptake is an early predictor of histologic response of osteosarcoma, Ewing's and soft tissue sarcomas to chemotherapy, and has correlated with clinical outcomes in Ewing's, soft tissue sarcomas and gastrointestinal stromal tumor.

SUMMARY

[18F]fluoro-2-deoxy-D-glucose positron emission tomography will likely play increasingly important prognostic and predictive roles in the management of sarcomas. Available data suggest that positron emission tomography is useful clinically in predicting response to therapy early in the course of treatment for both cytotoxic chemotherapy and kinase inhibitors. Additional study to determine the optimal semiquantitative measure of [18F]fluoro-2-deoxy-D-glucose accumulation in sarcoma and standardization of positron emission tomography methods is needed.

Impact of FDG PET for staging of Ewing sarcomas and primitive neuroectodermal tumours

AIM

High-grade Ewing sarcomas and Primitive neuroectodermal tumours (PNET) make up the tumours of the Ewing family. Our purpose was to evaluate the value of [18F]fluorodeoxyglucose positron emission tomography (FDG PET) in patients with Ewing tumours.

PATIENTS AND METHODS

Twenty-four patients who had PET because of a suspected Ewing tumour during a 5-year period were included in this retrospective study. The images of 33 whole-body FDG PET investigations performed in primary or secondary diagnostics were analysed visually and semi-quantitatively by using standardized uptake values (SUVs). In 14 cases, PET was compared to bone scintigraphy regarding bone lesions. The final diagnosis was based on histology, imaging and follow-up.

RESULTS

Histologically, the primary lesions were 10 Ewing sarcoma, 13 PNET and one osteomyelitis. The sensitivity and specificity of an examination-based analysis (presence of Ewing tumour and/or its metastases) were 96 and 78%, respectively. Altogether, 163 focal lesions were evaluated. Sensitivity and specificity regarding individual lesions were 73 and 78%. This lower sensitivity is mainly due to small lesions. In true-positive cases, the mean SUV was 4.54+/-2.79, and the SUVs in two false-positive cases were 4.66 and 1.60. True-positive and false-positive cases could not be differentiated definitively based on SUVs because of overlap and low values in true-positive lesions. In four cases, PET depicted 70 while bone scintigraphy depicted only eight bone metastases.

CONCLUSION

An FDG PET investigation is a valuable method in the case of Ewing tumours. PET is superior to bone scintigraphy in the detection of bone metastases of Ewing tumours. For the depiction of small lesions, mainly represented by pulmonary metastases, PET is less sensitive than helical computed tomography. Determination of the role of whole-body FDG PET in diagnostic algorithm needs further investigation.

CT appearance of bone metastases detected with FDG PET as part of the same PET/CT examination

PURPOSE

To retrospectively evaluate lesion findings at computed tomography (CT) performed as part of a combined positron emission tomography (PET)/CT examination in patients suspected of having metastatic bone lesions-lesions that were detected with fluorine 18 fluorodeoxyglucose (FDG) PET as part of the same examination-and to correlate the CT and FDG PET findings.

MATERIALS AND METHODS

This HIPAA-compliant study had institutional review board approval, and the need for patient informed consent was waived. Three hundred fifty-nine consecutive patients (191 male patients, 168 female patients; mean age, 56.9 years; age range, 8-92 years) underwent PET/CT. PET images were first reviewed by nuclear medicine physicians who had no clinical information regarding the presence or absence of bone metastasis by using a five-point grading system (0, a lesion was definitely negative for metastasis; 1, a lesion was probably negative; 2, a lesion was equivocal; 3, a lesion was probably positive; and 4, a lesion was definitely positive). For lesions assigned a grade of 3 or 4 at PET, CT characteristics such as the presence or absence of morphologic changes or accompanying findings (including bone destruction) were assessed by radiologists on the CT images obtained during the same imaging session.

RESULTS

One hundred seventy-nine lesions in 55 patients were considered to be probable or definite bone metastases at PET. One hundred thirty-three of these lesions in 33 patients were clinically confirmed to be bone metastases at follow-up and/or histopathologic examination. CT revealed osteolytic changes in 41 (31%) and osteoblastic changes in 21 (16%) of the 133 lesions, but no or nonspecific changes were seen at CT in 49 (37%) and 22 lesions (17%), respectively. Of the 179 lesions suspected at PET, 46 ultimately proved to be nonosseous or false-positive for bone metastasis. Of these 46 lesions, 38 were not located in the bone but in adjacent tissues such as the pleura.

CONCLUSION

CT images obtained as part of PET/CT scanning were useful in yielding the precise location of bone lesions and thus helping avoid misdiagnosis of bone metastasis; however, CT revealed morphologic changes in only half of the lesions assigned a grade of 3 or 4 at PET.

Diagnostic value of MRI in comparison to scintigraphy, PET, MS-CT and PET/CT for the detection of metastases of bone

The initial localization of metastases in the bone in patients with solid tumors has a relatively good prognosis in comparison with visceral metastasization. The early detection of bone marrow metastases allows for a rapid initiation of therapy and a subsequent reduction in the morbidity rate. Modern MRI is superior to the 30-year-old skeletal scintigraphy and bone marrow scintigraphy with respect to sensitivity, specificity, as well as the extent of osteal metastasis. MRI provides substantial, therapy-relevant additional information. MSCT plays an important role in the management of cancer patients in clinical routine and gives an excellent survey of the axial skeleton by demonstrating osteolytic and osteoblastic metastases. Extensive comparative studies of MRI with 18F-FDG-PET and 18F-fluoride-PET have not yet been carried out. Whole body MRI is a very promising new staging method for the oncological diagnosis of solid tumors and the detection of osteal metastases. The adoption of 18F-FDG-PET and 18F-fluoride-PET FDG as well as the side by side PET-CT image fusion and the two in one PET/CT examinations appears to be slightly less sensitive to whole body MRI in the detection of osteal metastases. Larger, prospective multicenter studies are necessary to establish these as new, promising methods for the detection of osteal metastases.